A process for the preparation of a 1,8-bridged 4-quinolone-3-carboxylic acid of the formula ##STR1## wherein the substituents are defined hereinbelow. Some of the compound are new. The old and new compounds are antibacterials and promote animal growth.
A new method for the synthesis of 7H-pyrido[1, 2, 3-de][1, 4]benzoxazine derivatives was developed. The method is characterized by the intramolecular cyclization of 1-(1-hydroxyprop-2-yl)-8-fluoro-4-quinolones which are prepared in three or four steps from ethyl 2, 3, 4, 5-tetrafluoro-benzoylacetate. As an application of this method, ofloxacin, an antibacterial agent, was synthesized.